Retroactive is an important word to know if you are taking psychology, government, law, or business courses. It's an adjective and in its most technical sense, it means that some current change also affects the past, for instance,

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The manager frowned when the employee asked if the union-won pay increase would be retroactive.

The telecom companies involved in eavesdropping on U.S. citizens managed to get themselves retroactive legal immunity. Thus it didn't matter how much evidence prosecutors found of past eavesdropping. The companies would not have to pay for current or previous misbehavior.

In contracts, it is important to indicate whether or not new clauses will or will not be applied retroactively.

Memory Peg: "Retro" is a Latin prefix meaning "back" or "backward." Thus anything that gets labeled "retroactive" has to have an effect on times past.

For a visual image of retroactive—and indeed for the prefix "retro" in general—imagine someone looking backward.

Specialized Use in Psychology: If you have ever studied something in the morning, thought you really understood it, and discovered by the next day that the information had become vague and muddled in your memory, then you have experienced what psychologists call retroactive interference. In other words, new memories came rushing into your brain and got in the way of memories formed during a previous time.

The good news is that you can avoid retroactive interference by

going to sleep right after learning new information. While sleeping your brain will work on storing the information in long-term memory.

over-learning new information to the point that you think you could easily explain it to someone else.

On the Less Technical Side:
The word has branched out in its uses and can also refer to feelings, attitudes, or behaviors that reach back in time, for instance,

My husband is as good as gold, and I know he loves me more than anything. But somehow I cannot get over my fierce retroactive jealousy. I keep thinking he still loves the girl he wanted to marry before she dumped him and he met me on the rebound.

Comprehension Checks

1. Given what you know about the word "retroactive," which of these sentences uses the word correctly:

The gallery offered a retroactive of the artist's work.

The clause would have a retroactive effect on prices paid in the past.

He needed to be retroactive in his response and not wait until tragedy struck.

2. Read the following statement and explain what governments and lawyers now consider "thinkable":

In his book The Rule of Lawyers, Walter K. Olson says that changes in the legal system "have made it thinkable (at least to some governments and lawyers) to impose retroactive liability today for business decisions in the 1920s that were clearly lawful at the time."